Headlight reflector



'aire CROMWELL A. B. HALVGRSON, JB?, 0E' LYNN, MASSCHUSET'S.

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Specification ot Letters Patent.

Patentes een; t', ieee.

.application le January 17, 1921. Serial No. 437,697.

automobile headlights on country roads, 'and' to direct a portion of the reflected rays i downwardly to make the light non-glaring for city use or when approaching parties moving in the opposite direction'. l ac-.

complisli this result by providing tivo relecting surfaces of revolution 'adapted to reilect rays arallel to their aires from a source of lig it in their respective foci, ar*-l ranged with their axesparallel and their focal planes coincident. These surfaces are arranged to be relatively displaced but with their axes parallel at the Will of the operator, and a source of light is located in the focus of the reflecting surface in front of the common focal plane'. For long distance illumination, the reflecting surfaces are arranged with their loci coincident, in which position parallel rays only are refiected. For anti-glare illumination, the surface locatedin back of the local plane is displaced downwardly, with its axis parallel to the axis of the front surface, in which position the rays of light striking the back surface are reflected downwardly. This structure is similar to that shown in my co'- pendin'g application for Letters Patent, Serial No. 437,698, led'danuary 17, 1921, which, however, due to the i'ixed relation of its elements, accomplishes a diderent result.

ll/iy invention will be better understood from the following description when taken y in connection With the accompanying drawina the appended claims. f

Us and its scope will be'pointed out in' 2 is a vievv similar to Fig. 1 illustrating another forml which my reflector may assume.

Referring to Fig. 2 of the drawings, the numeral 10 indicates a lamp casing, which Amay be of any conventional type, in which se is suitably mounted a reflector 11.

The reflector 11 is formed lof two reflecting surfaces 1 2, 18, of the saine focal length, each adapted to direct beams arallel to its axis from a lsource of light p aced at the locus. te

Thesev surfaces may he sections from. one paraboloid or from duplicate paraboloids having the same local lengths.

The reflecting surfaces are cut substantially through their focal planea-that is, on id a line perpendicular to their axes passingL Y through their foci, as indicated by the line "M 1r-a'. rllhe surface 12 is formed from that portion oi its parabola in front of the focal plane, and the surface 13 from the portion in in back of the focal plane, and the two sur faces are arranged edge'to edge with their focal planessubstantially coincident. 0bviously, by this arrangement the axes di the `reflecting surfaces may either coincide or sa be parallel.

The back reflector 13 is arranged to slide up and down in a vertical plane, with its axis parallel. I preferably accomplish this movement with an electromagnet 11i which as is suitably mounted Within the casing lll, and secured outside ol the suriijpe 13 and With its armature connected with that sur face at 15, in any suitable manner.

A suitable source 'of light is located in the no employ an incandescent lamp having a nes centrated filament mounted in the side of the reflector. lt is, of course, .understood that a point source oi light is not available; hmvever, in order to illustrate the direction ol' reflected rays, it is convenient to regard loe the light source 1.6 as a point source.

The line 17 indicates the axis of the front surface l2. Any rays of licht, say the rays 1S, 18 proceeding from the source 16, which strike the front reecting surface 12, are re- 10a flccted parallel to its axis 17, in accordance with Well known laws governing redaction from parabolic surfaces, as indicated by the reflected rays 19, 19. li now the electro magnet la be energized, in which case it is El@ arra gedlto move the back -reflectingsurface 13 upwardly, so that its axis 20 coin 'f cides with vthe axis 17 ofi-the front reliecting surface, all reflected rays will be parallel to their now common axis, in a manner readily understood, since their foci now coincides and the light source 16 is located in their now common focus. By deenergizing the electroma'gnet, the back surface 13 is allowed to drop to a lower position, with its axis 20 parallel with but below the axis 17, as shown in the drawings. In this position, the reflected rays from the front surface 12 are notchanged. -With respect to those rays of lightswhich strike the back surface 13, any ray directed upwardly, say the ray 21, apparently comes from a point 22 located on its axis 2 0 in front of the focal plane, and' such rays are therefore Adirected convergently with the axis, i. e., downwardly, as indicated by 'the reflected ray 21. Any ray striking the surface 13'downwardly, sayv the ray 23, passes through its axis 20,'-1nd ap.

.v 'parten/tlv comes from a point 24 on said axis in nach ofthe focal plane, and such rays are diecte'd diver-gently from the axis, i. e., downwardly, as indicated by the reflected ray 23",

ln another.: forni of my invention, the Lack refiecting surface 13 may be provided with av suitable opening arranged to receive a Mangin mirror 25, having the same focal length as the surface 13, and with its axis coinci dent with the axis 20 of said surface, as

shownIk in Fig. 1. ln this structure, the rays of light striking the surfaces 12, 13 are 'reflected in the same manner as above described with reference to Fig. 2. With respect to the' rays of light strikingthe Mangin mirror 25;--when the electromagnet 14 is energized, -'in which position the axis of the Mangin mirror7 coincides with theaxis 17, such rays'are 'reflected parallel to said axis, in accordance with well known laws governing reflection from mirrors of this character. When the electromagnet 14v is deenergized, in. which position the axis of the Mangln mirror is pelow but parallel to the axis 17, an ray from the source 16 direct/ed upward say the ray 26, apparently comes from a point 27 located on its axis in front of the focal plane, and such rays are reflected downwardly, as indicated by the ray 26. Any ray from the source directed downwardly toward the Mangin mirror, say

- the ray 28, passes through its axis, and apparently comes from a point 29 on said axis land no portion of the other reflectin long distance illumination. By deehergizing the electromagnet, the surfaces are relatively displaced with the axis of the back surface parallel with and below the axis of the front section. In this position, all rays reflected from the surface in back of the focal plane are directed downwardly, the condition desired for anti-'glare illumination. lVith respect to the parallel rays reflected from the front surface, in the anti-glare position of the back )art of the reflector, it is found in practice tliat these are not sufficient to cause inconvenience, since the greater portion of thc reflected rays proceeds from in back of the focal plane. It is, of course, understood that the operation of the electromagnet could be reversed, so that when denergized, long distance illumination is obtained and when energized a nonglare condition exists. i

While I have described my invention as embodied in concrete form in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto, since various modifica,-

'tions thereof will suggest themselves to-thosc surfaces of revolution arranged with their 1,05

axes parallel, and with their focal planes coincident, n o portion of one of said reflecting surfaces being back ofthe fccalrplane and no portion 'of the other reflecting surface being ahead of the focal plane, and/11,0 means for relatively displacmg saidrefiecting surfaces with their axes parallel anc/l//f' their focal planes remaining coincident. l,

3. A reflector comprising two reflecting surfaces of revolution arranged with'their axes parallel, and with their focal planes coincident, no portioncf one of said reflecting surfaces being back of the focal planes surface being ahead of the focal plane, and means for relatively displacing said reflect ing surfaces with their axes parallel and in back of the focal plane, and is also retheir focal4 planes remaining coincident, in

energizing the electromagnetA 14, the foci of l the.Y front and back reflecting surfaces are caused to coincide, giving reflected rays parallel to their axes, a condition'desired for combination with a source of light in the 'focus of the surface in front ofthe focal angin m1rrorfixed-in and constituting i3@ an element of the part back of the focus,

Said ars being arranged with the axis of the ldilrgin'mirror and the axis of the Snr-- face in front of the foe-us parallel, and means for relatively displacing said parts with said axes parallel and their'focal planes remain-y ing coincident. l

5. A reflector comprising a parabolic refleeting surface cnt into two parts on a line perpendicular to its axis tlirou'glithe focus, a Mangin mirror fixed in and cnnstituting an elemeny of .the nari; backnf the focus, said URGMWELL A. HALVGRSN, Jr. 

